Quasi-equilibrium assumption in analytical models of thermoluminescence and its validity in practical cases

Thermoluminescence (TL) intensity I(T), Q(T) and P(T) as a function of temperature T during glow curve readout are calculated numerically for three types of physical models, where Q(T) is called the quasi-equilibrium (QE) function and P(T) is the ratio of the retrapping to recombination rates. The models include a one trap-one recombination centre (RC) and an interactive or non-interactive deep trap. The results lead to the following conclusions: (1) Under a wide variety of parametric combinations Q(T) ≅ 1 and P(T) » 1 is a more common condition than Q(T) ≅ 1 and P(T) « 1. (2) Glow peaks with first order character are obtained even when P(T) » 1 which is contrary to the Randall and Wilkins Theory. These two conclusions are in clear contradiction to the assertions of Lewandowski and McKeever that Q(T) ≅ 1 and P(T) » 1 are not self-consistent conditions and that the dominance of first order TL kinetics in nature is explained only with P(T) « 1. The paper also discusses the practical side of the QE assumption in relation to the real materials and infers that the QE condition is most likely to prevail in the TL emission of common phosphors.